The present invention broadly relates to a new and improved apparatus for sealing high pressure installations with respect to a liquid medium.
In its more specific aspects the invention relates to a new and improved apparatus for sealing a high pressure installation containing a movable member with respect to a liquid medium within a pressure space or chamber which is to be sealed. The movable member may be, for example, an oscillatory movable plunger or displacement piston in a high pressure pump or a rotary movable shaft in a high pressure apparatus.
A known high-pressure sealing apparatus or device for the displacement pistons of piston pumps is formed by a metallic sleeve surrounding the displacement piston located in a bore of the pump head in spaced relationship from the wall of . the bore in the pump head. The metallic sleeve comprises, at the low-pressure end thereof, a guiding flange situated within a bore which is cut or machined into the pump head and which is enlarged as compared to the pump head bore.
At high pressures in the range of several thousand bar, as required particularly in the case of pumps for fluid-jet operated cutting installations, the known high-pressure clearance seal has been found to be insufficient. The clearance sleeve comprises sections of different material thickness, so that, particularly in the case of strongly fluctuating pressure loads, material failures can occur. In addition, the service life of the known seals is unsatisfactory.
A high-pressure piston sealing apparatus as known; for example, from German Pat. No. 2,336,118, acts on the basis of a labyrinth seal. The labyrinth seal is formed by at least one sealing body which is structured as a sealing sleeve containing a labyrinth section and floatingly arranged on the piston. Apart from the expensive manufacture of the labyrinth arrangement such a seal has the disadvantage that it possesses an increased assembly length. Also, due to the great number of labyrinth tips which bear upon the piston, there is present a relatively high wear.
Furthermore, there are known high-pressure seals for the displacement pistons of piston pumps and pressure transmitters, wherein the sealing action is effected by means of a sealing ring made of a soft material and snugly fitted to the moved plunger due to the tensioning of an O-ring.
With respect to the encountered pressures the service life of the aforementioned known seal is unsatisfactory, since there is present relatively high wear due to the unavoidable formation of a gap or space between the plunger and the so-called back-ring or support ring of the sealing ring.